Patient selection and data collection
After obtaining approval from the review board of Chiba Nishi General
Hospital, we performed a prospective, observational study of data
collected from patients who underwent right mini-thoracotomy, which is a
minimally invasive surgery, at Chiba Nishi General Hospital between July
2014 and July 2018. All patients were diagnosed based on cardiac
catheterization and echocardiography findings. During the study period,
there were 273 patients who underwent MICS and MRI, including
diffusion-weighted imaging (DWI) sequences, the day before and 5 days
after surgery. We selected the femoral artery for retrograde perfusion
and the axillary artery or ascending aorta for antegrade perfusion.
Preoperative computed tomography (CT) angiography was routinely
performed, and vascular pathology was evaluated.
The femoral artery was chosen as the cannulation site if the patients
met the following criteria: 1) no calcification in the entire
circumference of the aorta, 2) thrombosis in less than one-third of the
aorta, and 3) thrombosis in the aorta with thickness <3 mm. In
patients who did not meet the criteria, antegrade cannulation was
performed.
Of 273 patients, 175 (64.8%) underwent femoral cannulation for CPB and
95 (34.4%) axillary arterial cannulation. Moreover, one (0.37%)
patient had both femoral cannulations, 1 patient (0.37%) femoral and
axillary arterial cannulations, and remaining 1 patient (0.37%)
ascending aorta cannulation. Patients who underwent axillary arterial
cannulation, both femoral and axillary arterial cannulations, and
ascending aorta cannulation were excluded. Moreover, one patient who
presented with a subdural hematoma 3 days after the surgery was
excluded. Finally, 174 patients were included in the study (Figure 1).
Patients who were scheduled for right mini-thoracotomy underwent MRI,
including DWI sequences, the day before and 5 days after surgery. SBIs
detected via DWI were categorized as follows: A) 1–3 DWI spots
measuring <10 mm, B) >3 DWI spots measuring
<10 mm, and C) single DWI lesion measuring >10 mm
(Figure 2).
A high field strength (3T) MRI unit was used. The protocol included
axial T2-weighted imaging, axial T2-weighted fluid attenuation inversion
recovery imaging, axial trace-weighted DWI, and apparent diffusion
coefficient mapping.
All images were evaluated by a diagnostic radiologist. When lesions were
detected, neurosurgeons were consulted. Renal failure was defined as the
requirement of hemodialysis or an elevated creatinine level at 2.0
mg/dL, which is two times the preoperative baseline level. Thirty-day
mortality was defined as all deaths within 30 days after surgery
regardless of where the patients died (in- or out-of-hospital).